Control of gaseous emissions from livestock operations is needed to ensure compliance with environmental regulations and sustainability of the industry. The focus of this research was to mitigate livestock odor emissions with UV light. Effects of the UV dose, wavelength, TiO2 catalyst, air temperature, and relative humidity were tested at lab scale on a synthetic mixture of nine odorous volatile organic compounds (VOCs) and real poultry manure offgas. Results show that it was feasible to control odorous VOCs with both photolysis and photocatalysis (synthetic VOCs mixture) and with photocatalysis (manure offgas). The treatment effectiveness R (defined as % conversion), was proportional to the light intensity for synthetic VOCs mixtures and followed an order of UV185+254 + TiO2 > UV254 + TiO2 > UV185+254; no catalyst > UV254; no catalyst. VOC conversion R > 80% was achieved when light energy was >~60 J L−1. The use of deep UV (UV185+254) improved the R, particularly when photolysis was the primary treatment. Odor removal up to ~80% was also observed for a synthetic VOCs mixture, and actual poultry manure offgas. Scale-up studies are warranted.

Aerial emissions of odorous volatile organic compounds (VOCs) are an important nuisance factor from livestock production systems. Reliable air sampling and analysis methods are needed to develop and test odor mitigation technologies. Quantification of VOCs responsible for livestock odor remains an analytical challenge due to physicochemical properties of VOCs and the requirement for low detection thresholds. A new air sampling and analysis method was developed for testing of odor/VOCs mitigation in simulated livestock emissions system. A flow-through standard gas generating system simulating odorous VOCs in livestock barn emissions was built on laboratory scale and tested to continuously generate ten odorous VOCs commonly defining livestock odor. Standard VOCs included sulfur VOCs (S-VOCs), volatile fatty acids (VFAs), and p-cresol. Solid-phase microextraction (SPME) was optimized for sampling of diluted odorous gas mixtures in the moving air followed by gas chromatography-mass spectrometry (GC-MS) analysis. CAR/PDMS 85μm fiber was shown to have the best sensitivity for the target odorous VOCs. A practical 5-min sampling time was selected to ensure optimal extraction of VFAs and p-cresol, as well as minimum displacement of S-VOCs. Method detection limits ranged from 0.39 to 2.64ppbv for S-VOCs, 0.23 to 0.77ppbv for VFAs, and 0.31ppbv for p-cresol. The method developed was applied to quantify VOCs and odorous VOC mitigation with UV light treatment. The measured concentrations ranged from 20.1 to 815ppbv for S-VOCs, 10.3 to 315ppbv for VFAs, and 4.73 to 417ppbv for p-cresol. Relative standard deviations between replicates ranged from 0.67% to 12.9%, 0.50% to 11.4%, 0.83% to 5.14% for S-VOCs, VFAs, and p-cresol, respectively. This research shows that a simple manual SPME sampler could be used successfully for quantification of important classes of odorous VOCs at concentrations relevant for real aerial emissions from livestock operations.

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Livestock production systems are associated with aerial emissions of odor, volatile organic compounds (VOCs), other gases, and particular matter including airborne pathogens. Control of those emissions is needed to assure compliance with environmental regulations and long-term viability of the industry. The focus of this research is a novel approach to abatement of livestock odor and pathogens utilizing photocatalysis, i.e., UV irradiation in presence of TiO2 as a catalyst. A standard gas generation system was built and tested to generate ten odorous VOCs commonly defining livestock odors. These VOCs included methylmercaptan, ethylmercaptan, dimethylsulfide, butylmercaptan, acetic, propanoic, butyric, and isovaleric acid, p-cresol, and H2S. Our previous research established a reduction of VOCs with UV light only of 60~98% for sulfur VOCs and 91% for p-cresol, but only 20 to 45% removal for volatile fatty acids (VFAs). Titanium dioxide was used in the current research to catalyze UV reactions in the same gas mixtures of VOCs held in a small photoreactor. The reactor was designed to conduct controlled tests with UV light under dynamic (with airflows) conditions that facilitate experiments simulating exhaust from mechanicallyventilated barns. Six 10W lamps with characteristic bands at (185), 254, 312, 365 nm, respectively, and principle output at 254 nm were used as UV source in dynamic system. Solid phase microextraction (SPME) fibers were used to sample VOCs before and after UV treatment and for transfer of samples to a gas chromatography and mass spectrometry olfactometry (GC-MS-O) system. Odor analysis was completed by a forced-choice dynamic-dilution olfactometer in the Olfactometry lab at ISU. Effectiveness of four different treatment options, i.e., UV254, UV185+254, UV254+TiO2, and UV185+254+TiO2 was assessed. Effect of light energy, catalyst presence and light wavelength was evaluated. More than 50% in chemical reduction was found for all VOCs tested with a treatment time of 18.5 second. A linearly positive correlation was found between the percent conversion of tested VOCs and light energy dose. TiO2 showed to greatly improve the treatment effectiveness on VOCs, VFAs in particular, no matter deep UV was used or not. However, when TiO2 was used, deep UV showed very little improvement in degrading VOCs tested, while significant improvement was observed when no TiO2 was used. Total odor reduction of 70% by certain energy level indicated the feasibility of odor mitigation by UV light. Continued work includes simultaneous inactivation of airborne pathogens with UV light.